Furnace grate



June 19, 1934. H. B. HOLT 1,963,789

FURNACE GRATE Filed July 13. 1932 3 Sheets-Sheet l WITNESSES H M 5 #M 0. 61M H 5M am 7142344 June 19, 1934. H. B. HOLT 1,963,789

Patented June 19, 1934 UNITED STATES PATENTOFFICE FURNACE GRATE Harris B. Holt, Pittsburgh, Pa. Application July 13, 1932, Serial No. 622,198

. 4 Claims. (01. 110-40) The invention relates to furnace grates, and more'particularly to traveling grates of the endless chain or belttype, which, by their movement, carry into a furnace new supplies of fuel, 15 or of other material to be burned, and carry away the ashes remaining after'combustion.

In the conventional type of traveling grate the fuel-supporting surface of the endless belt is formed from a plurality of grate bars mounted 1 in rows extending transversely thereof. These rows are maintained in substantial contact with one another while the portion of the belt supporting them is traveling in a straight path through the furnace and, therefore, present'a continuous fuel-supporting surface. However, a disadvantage common to such'grates is that'as any given portion of the belt reaches the end of its straight path and comes to the curved end of its course where it starts to return to the opposite end of the furnace, the rows of grate bars supported on that portion are spread apart as they traverse the curve. The spreading of the rows breaks the formerly continuous fuel-supporting surface of the grate, thereby permitting refuse, such as hot ashes, cinder and unburned matter, to fall into V-shaped crevices between the rows and to reach the underlying chain which is apt to be damaged by the heat. Furthermore, as the grate enters its straight return path and the rows of grate bars close up, some of the refuse may be entrapped and compressed between the bars. When hard particles form a part of the entrapped material, such as in rubbish incinerators where nails, solder from tin cans, other metal, and the like fall between the rows, the bars tend to be pried apart and broken from their supports, and the belt itself may be broken, which necessitates shutting down the furnace or incinerator while the grate is being repaired.

It is among the objects of this invention to provide a traveling chain grate which presents a continuous unbroken fuel-supporting surface at all points in its path of travel, tends to-permit ashes caught between its grate bars to escape therefrom, is simple in construction, comparatively light in weight, and easy to repair.

The preferred embodiment of the invention is illustrated in the accompanying drawings, of which Fig. 1 is a fragmentary plan view of an endless grate shown partly in section and with some of the grate bars removed; Figs. 2 and 3 views taken on the irregular lines 11-1]: and III-III, respectively, of Fig. 1; and Fig. 4 a side .55 view of the grate mounted in operating position,

but with the outermost strand" of the outside chain removed, and with its center portionbroken away. Y P

In accordance with the invention there is provided an endless chain grate comprising a belt carol formed of links arranged in transverse parallel rows and pivotally connected at their ends. Grate bars are arranged in transverse parallel rows corresponding in number to the rows of links, and are serially disposed with overlapping ends, and means are provided for connecting the bars to the belt and for positioning each row of bars rigidly with relation to one rowof links. To insure that the grate will present a continuous unbroken fuel-supporting surface throughout its course, the overlapped ends of the bars of each row are formed to lie in a cylindrical surface coaxial with a pivot axis of the row of links positioning that row of bars and continuous with and forming an extension of the fuel-supporting surfaces of the bars of said row.

Referring'to the drawings, a traveling chain grate is shown as being formed of two general parts, an endless chain or'belt l, and fuel-sup; porting grate bars 2 mounted thereon. The preferred construction of the belt is best illustrated in Fig. 1 where the belt is shown as comprising a plurality of parallel chains 3 retained in spaced relation by means of long and short spacing members or gratebar supports, 4 and 5 re- 5 spectively. The chains are preferably of the double strand type'formed from a plurality of links 6 pivotally connected at their ends by flattop pivot pins '7, both strands of each chain being connected by the same pins to bring their respec- 99 tive pivot axes into alignment.

' While the belt may travel in either direction, the preferred direction of travel is that indicated by the arrows on Figs. 2 and 4. The pin-receiving opening 8 in the rear of each link is cylin- 9. drical to permit the link to pivot on its pivot pin, but the pin opening 9 in the forward end of each link is shaped" to conform to the cross-sectional contour of a pivot pin, the flattened wall of the opening being at the top of the link as viewed 00 in Figs. 1 and 2. The pivot pins are thus prevented from rotating in the forward ends of each pair of links, but the adjoining links, through whose rear openings 9 the pins also .extend, are permitted to pivot thereon; U1

A plurality of the grate bar supports 4 and -5 serves to retain the chains and their strands of links in predetermined spaced parallel relation, thereby completing the belt. The short supports 5 have tubular body portions lO dis- 11.0

posed between and spacing apart the strands 3 of each chain with the pivot pins '7 extending therethrough, and the long supports 4 have tubular end portions 11 into which the ends of pins in adjacent chains project. The side of the body portion between the tubular ends of each long support is open, as at 12, to give access to the pivot pins projecting into it so that they may be driven out or replaced should the belt require repairing, andlalso to eliminate unnecessary weight. Each of the grate bar supports is provided with an integral radial rib 13 projecting outward from the belt and having oppositely disposed side flanges 14 extending therefrom, the

ribs of the short supports projecting across the' pivoted ends of the adjoining links to substantially meet the ribs of the long supports and thereby form a continuous grate bar support.

Each short support is provided with a, centrally located threaded opening 15 extending from its pin-receiving opening outward through its radial rib 13,v and each long support isprovided with a similar opening in each end portion 11. Short screws 16 register with these openings and are turned down onto the flattened portions of the underlying pins'thereby not. only preventing the grate bar supportsfrom rotating on the pivot pins, but also preventing the strands of the chains from pulling away from one another. It should be apparent from this construction that the pivot axes ofeach pair ofchains are maintained in alignment with the pivotaxes of the other pairs of'ch ains, all of the pins and links thus being arranged parallel rows transversely of the belt. A I. Aplurality of fuel-supporting grate bars 2 is slidably mounted on each row of grate bar supports, the under side of each barbeing provided with a transverse recess 18 for receiving the flanges 14 of the radial rib 13 of a grate bar sup-v port, and with inwardly projecting lugs 19 -engaging-the under surface of flanges 14 to prevent the grate bar from moving transversely of its support. A row of grate bars mounted on a grate bar support is held in place thereon at each end bya bevelled-top bracket 21 (Fig. 3) engaging'a correspondingly bevelled lower surface of the outermost grate bar 2 2, the bracket being detachably connected to,the rip of the adjoining grate bar supportby means of a nut 23; which engages a threaded pin 24 whose inner end projects through an aperture in the bracket and isthreaded into anopening in the rib, The. lower portion of this bracket is provided with an opening 25 through which the outerend-of the adjoining pivot pin projects, the bracket also having a backward extension 26 provided with an outwardlyextending fiange 2 7 for a purpose to be described below. v w 7 j The outermostgrate bars 22 are'wider than the other bars, and project laterally from the belt and beyond the retaining nuts and bolts beneath them. Asall the gratebars are slidably mounted onthe support, and as space is left between them to allow for heat expansion, itis desirable-that inward sliding movement of the end'bars 22 be limited to prevent them from be ing' moved inward where they would expose'the sides of the belt and crowd" all the intermediate bars together. Therefore, there are provided retaining strips 30', best shown in Fig. 3, having depending extensions 31 projecting into the threaded openings 15in the support ribs,' and extending longitudinally along the outer faces of the ribs in transverseslots 32 in'the inner walls of the support-receiving recesses 18 of the grate bars. The outer end of each retaining strip is adapted to be engaged by the outer grate bar, While the connected depending extensions of the strip serve to lock the adjoining long and short supports together in case the short screws 16 should loosen. Similar strips may be associated with the center pair of chains where they look the associated grate barsuppor-ts. together.

, As clearly shown in Fig. 4, theen'dless grate thus formed is disposed in a furnace in such manner'that the upper and lower lengths of the belt lie in vertically spaced substantially horizontal planes with the connecting curved end portions passing around sprockets 35 and pulleys 36 at the front and rear of the furnace, respectively. The path of travel of the belt when the sprockets are revolving is, therefore, in a horizontal plane from the front to the rear of the furnace, then downward in a curved path around the pulleys, back toward the front of the furmice in' a horizontal plane, and up in a curved path around the sprockets to its upper. plane.-

To prevent the grate from sagging between the sprockets and. pulleys, its lower portionis sup: ported on rails 37 along which the grate-bars slide, and the upper portion is supported on a plurality of slide plates 38 extending longitudinally of the grate (Fig. 3) between the sprockets and pulleys. The slide plates are secured tothe upper flanges of a plurality of transverse I-beams 38a fastened at theirends to the vertical side walls 3817 which form a housing for the grate. Vertical guide plates 40 are connected to the re fractory furnacewalls 39 above thehousing walls, and: extend from the top of the belt substantially to the slide plates below. The smallamount of fuel and ash that works down between the edges of the grate and the guide plates falls upon the outer slide plates. where it is immediately scraped along and oif the ends thereof by means ofthe flanged backward extensions 26 of the bar-- retaining brackets 21. 1 p 'Although the endless grate has beendescribed asit is shown in the drawings, it is not, of course, necessary that it be constructed in precisely this manner. The essence oftheinvention lies principally in the shapeof the grate bars which are designed in such-a manner as to overcome the defect inherent in prior endless chain grates, namely, the spreading apart of the rows of grate bars as they travel the curved ends of-their path, which breaks the continuous fuelbearing surface of the traveling grate and permits foreign matter to enter between the rows.

To this end, the bars of each roware so constructed as to overlap the fuel-supporting surfaces of the bars of the next-preceding row; Furthermore, the overlappedend portion of each bar is formed as an arcuate portion of a cylindrical surface coaxial with the axis of the row of pivot pins on which is-mounted the grate bar support that supports that particular gratebar. 'Als0,;-that particular row of pivot pins is the samerow of pins that connects the links, positioning the overlapped bars, tothe links with relationto which the adjacent row of overlapping bars is rigidly positioned. In other words, thefuel-supporting surfaces 41 (Fig. 4) of the overlapped ends of the bars in each row are formed as an arcuate portion of a cylindrical surface coaxial with the common pivot axis of the row of'lin'ks positioning that row of bars and the row of links positionin'g'the-ad jacent overlappingrow of bars. Thus,'whe'n the belt rounds acu'rved end of its path-, any' given row of links, with the grate bars rigidly positioned by it, pivots at its rear end on an axis which is also the axis of a cylindrical surface in which lie the overlapped ends of the'next preceding row of bars. Consequently, the rear or overlapping ends of the bars of the first row turn in an arc concentric with the curve of the fuel-supporting surfaces 41 of the forward or overlapped ends of the bars of the preceding row, and it follows that the two rows of bars are not separated and that the fuelsupporting surface of the grate remains continuous and unbroken throughout its length. It is desirable that the lower surface 42 of the overlapping portion of each bar be curved to conform to the arc in which it turns in order that a gap will not be formed between the ends of adjacent bars in case the overlapping end of a bar is burned away by the intense heat from the overlying fuel. The bars are provided with the customary draft slots 43, and, aside from their curved ends, may be made in any desired form,

By reference to the portion of the grate shown in Fig. 4 as being disposed on the sprockets, it is seen that if any foreign matter has worked itself between the grate bars it will tend to escape therefrom, as the bars travel upward around the sprockets, through the slight clearance space 44 existing between the rows. Therefore, the grate is moved in the direction of the arrows in preference to the opposite direction in which the bars would tend to retain such foreign matter between them, although it may be moved in the opposite direction.

As the belt is not constructed of a solid web of links, but is formed from a few strands of chains connected together by grate bar supports, it is light in weight. In addition, by reason of the decreased number of links, there are less parts to become defective, and ready accessibility is given to all parts of the belt for inspection or repair. However, due to the fact that the fuelsupporting surface remain unbroken, the likelihood of the grate becoming defective is greatly reduced.

According to the provisions of the patent statutes, I have explained the principle and mode of operation of my invention, and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. An endless chain grate, comprising a belt formed of links arranged in transverse parallel rows and pivotally connected at their ends, grate bars arranged in transverse parallel rows, the rows of grate bars corresponding in number with said rows of links, said bars being serially disposed and having overlapping ends, and means for connecting said bars to said belt and for pcsitioning each row thereof rigidly with relation to one row of links, the fuel-supporting surfaces of the overlapped ends of the bars in each row being formed as an arcuate portion of a cylindrical surface coaxial with the axis on which the row of links positioning said. row of bars and the row of links positioning the adjacent overlapping row of bars pivot relatively to each other.

2. An endless chain grate, comprising a belt formed of links arranged in transverse parallel rows and pivotally connected at their ends, grate bars arranged in transverse parallel rows, the rows of grate bars corresponding in number with said rows of links, said bars being serially disposed and having overlapping ends, and means for connecting each of said rows of bars to said belt and for positioning the row rigidly with relation to one of said rows of links, each row of bars being disposed parallel to the axis on which the row of links positioning said bars and the row of links positioning the adjacent overlapping row of bars pivot relatively to each other, the fuel-supporting surfaces of the overlapped ends of the bars in said row being formed as an arcuate portion of a cylindrical surface coaxial with said axis.

3. A traveling chain grate, comprising a plurality of spaced endless chains advancing in parallel paths and formed of links pivotally connected at their ends with the pivot axes of all the chains in parallel alignment, grate bar supports disposed in parallel relation with each of said supports connected to one row of links and positioned rigidly in relation thereto, a plurality of grate bars reznovably mounted in a row on each grate bar support with one end of their fuelsupporting surfaces overlapping the ends of the grate bars in the next preceding row, and detachable means fcr locking said bars on said supports, said overlapped ends of the bars of each row being formed as an arcuate portion of a cylindrical surface coaxial with the axis on which the rows of links positioning said row of overlapped bars and the adjacent row of overlapping bars pivot relatively to each other, whereby a continuous unbroken fuel-supporting surface is presented by the grate at all points in its path of travel.

4. A traveling chain grate comprising a plurality of endless chains advancing in parallel paths and formed of links pivotally connected at their ends by pivot pins aligned in parallel rows, the aligned pins in one end of the links of each of said rows being secured against rotation therein but being journalled in the adjoining ends of the links of the adjoining row, grate bar supports rigidly mounted on said pins and spacing said chains apart, a plurality of fuel-supporting grate bars slidably mounted on each grate bar support with one end overlapping one end of the fuelsupporting surface of the plurality of grate bars in the next adjacent row, and detachable means for retaining said bars in place on said supports, the opposed faces of said overlapped and overlapping ends of the grate bars in said adjacent rows being formed as arcuate portions of concentric cylindrical surfaces coaxial with the axis of the row of pivot pins connecting the rows of links positioning said adjacent rows of grate bars.

HARRIS B. HOLT. 

